<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>测试class</title>
    <style type="text/css">
        .b {
            background-color: red;
        }

        .a {
            background-color: gold;
        }

        .c {
            background-color: chocolate;
        }

        .d {
            background-color: black;
        }
        div {
            width: 100px;
            height: 100px;
        }
    </style>
</head>
<body>
    <div class="c b d">

    </div>
</body>
</html>